1. Field of the Invention
This invention relates to a novel process for obtaining an accurate, or representative, sample of gas from a system containing solid particulate material, a gas, water and steam and a novel apparatus therefor.
2. Description of Prior Art
When coal is to be burned in a furnace, it is first passed through a pulverizer to obtain coal particles of a size suitable for burning in the furnace. From about 15 to about 20 percent of the air required for combustion in the furnace is also introduced into the pulverizer to transport the coal particles thereto. In some cases, the air introduced into the pulverizer also helps to dry the coal therein. Since coal contains some water, water will also be present in the pulverizer system.
Because of the relatively high oxygen content in the pulverizer and the tendency of coal particles to agglomerate therein, there is a potential for an explosion therein. When such danger arises, the system in the pulverizer can be rendered inert by the introduction therein of sufficient steam to reduce the oxygen content to about nine volume percent, or less, within about two to about four minutes. In order to make sure that the oxygen content of the mixture in the pulverizer is below the desired amounts, it is necessary to obtain accurate and rapid measurements, of the contents of the pulverizer, particularly the oxygen content.
Unfortunately, instrumentation presently installed in commercial coal pulverizers for measuring the oxygen content in such pulverizers does not provide reliable readings therein after the introduction of steam. During the inerting procedure, the walls of the pulverizers and the instrument tubing therein remain at temperatures significantly lower (about 120.degree. F.) than the saturation temperature of the air-steam mixture flowing through the central, or main, portion of the pulverizer. Consequently, due to the resulting condensation of some of the steam, the partial pressure of the steam in the sample reaching the oxygen analyzer cell is significantly lower than that existing in the pulverizer for the steam (about 50 volume percent) and therefore results in an inaccurate reading therefor. In addition, the resulting condensate causes sedimentation of the local particles, resulting in reduction of flow of the air-steam stream to the oxygen analyzer cell, further degrading the sampling operation.